1. Field of the Invention
The present invention relates to an amorphous alloy, a molding die including the amorphous alloy and used in a method for producing camera lenses and the like, and a method for molding an optical element using the molding die.
2. Description of the Related Art
The present invention relates to a molding die used for producing optical elements such as a lens, a prism, and the like by press-molding glass materials.
A press-molding technique for glass materials without the need for a grinding and polishing process is a simple production process capable of simply producing lenses at low cost. Therefore, the press-molding technique has recently been being used for producing not only lenses but also prisms and other optical elements in general.
Examples of properties required for mold materials used for producing such glass optical elements by press-molding include excellent heat resistance, chemical stability, hardness, releasability, workability, etc.
In addition, there have been many proposals of molding dies. For example, U.S. Pat. No. 4,629,487 proposes a molding die produced by processing cemented carbide having excellent heat resistance, oxidation resistance, and hardness into a desired shape and then coating a surface with a noble metal having chemical stability and high releasability from glass materials to form a release film.
However, in order to realize a variety of optical designs, various glass materials have recently been being used for glass elements. Some of the glass materials contain high-reactivity components such as phosphoric acid, hydrofluoric acid, and the like, and release films for molding dies with higher releasability are required for stably molding such glass. Therefore, US Patent Laid-Open No. 2009/23694 proposes a glass molding die using an amorphous alloy, the mold being capable of achieving chemical stability and high releasability.
However, a release film of the molding die described in US Patent Laid-Open No. 2009/23694 is chemically stable but has low hardness because it includes a cut layer. In addition, a PtHfZrNi amorphous alloy described in US Patent Laid-Open No. 2009/23694 has a value of hardness of 12 GPa measured with a nano-indenter manufactured by Agilent Technologies, Inc.
During glass molding, dust rises from a sliding portion of a molding die or apparatus. Carbide used as a mold material has a hardness of about 13 GPa to 18 GPa. In contrast, when a coating used for a molding die has a hardness of about 12 GPa as described above, such carbide dust is often caught by the mold during molding, thereby damaging the coating. When a glass optical element is molded with such a damaged molding die, damage of the molding die is also transferred to the glass optical element, causing defects in the appearance of the glass optical element.